1. Field of the Invention
The present invention relates to an electrophotographic copying apparatus which is capable of reproducing an image represented by an electric signal. More particularly, the invention concerns a copying machine which incorporates a function of reproducing electric signal information available in facsimile or like equipment as a visible image in addition to the normal copying function of a conventional electrophotographic copying machine.
2. Description of the Prior Art
Both electrophotographic copying apparatus and facsimile equipment tend to be increasingly and widely employed for the purpose of enhancing efficiency in the communication of information in the business world. In this connection, it is however noted that facsimile equipment, which is usually more expensive than electrophotographic copying apparatus is in practice used at less frequency than the latter, which provides a great obstacle to expansion of use of the facsimile. Besides, hitherto known facsimile equipment suffers from various drawbacks. That is, the reproduced image is of a remarkably degraded quality despite the necessity to use a recording paper which has undergone specific treatments in the case of facsimile equipment of an electric discharge recording type. In addition, a high recording speed can not been attained, and an unpleasant smell is produced. Facsimile equipment of the thermal recording type is also disadvantageous in that a specific recording paper is required, the recording speed is low, and so forth. Although the electrostatic recording type equipment utilizing a discharge effect except for the discharge breakdown can enjoy a higher recording speed and an improved image quality as compared with the first and second mentioned equipment, there are disadvantage in that a specific recording paper is still required to be used and the equipment is quite expensive.
Under the circumstances, it is desirable to adopt, if possible, the electrophotographic copying system which allows the image reproducing treatments to be carried out rapidly in a facilitated manner with a greatly simplified structure. However, in consideration of the fact that a lot of time is required for receiving and processing the facsimile, the electrophotographic copying principle can not be straightforwardly applied to facsimile equipment, because there is an incompatibility in speeds between the electrophotographic copying operation and the facsimile signal receiving and processing operation. The former operation can be effected at a high speed, while the latter operation is attainable only at a relatively low speed.
As an attempt to eliminate the drawbacks of facsimile equipment such as low frequency of use, need for the specifically treated recording paper and so forth, it is conceivable to produce an image on a cathode ray tube CRT from the facsimile signal and then to project the CRT screen image onto a photosensitive medium of an electrophotographic copying apparatus in a similar manner as the image of an original to be copied is projected, thereby to visualize and record the electrical signals incoming from the facsimile equipment. This approach is advantageous over the hitherto known facsimile systems in that the screen image on the CRT can be electrophotographically copied. However, the main problem in that the visualising or copying treatment is inhibited during the reception of the facsimile signal which takes a lot of time-remains to be solved.
The above problem may be solved by storing the facsimile signals in an electric memory device and reconstructing the image on the basis of the information stored in the memory. However, this approach in turn requires a memory of a large capacity, involving ultimately high expenditure for the whole system.